Some profilometers work in an interferometric mode to determine a height map of an object. These profilometers are suited for measuring tasks where an extreme high height resolution is required independently of the magnification of a microscope objective. However, in the interferometric mode, the profiler may be limited to measuring relatively smooth surfaces when used with low magnification objectives.
Other profilometers work in a non-interferometric mode. These profilometers include a microscope, which can be used as an optical sectioning microscope in a confocal microscope or as an optical sectioning microscope in a structured light illumination microscope (SIM). Confocal or structured illumination microscopes (SIM) are suited for measuring a height profile of structured surfaces in a low magnification range and generally provide better results when measuring steep slopes. Typically, non-interferometric optical sectioning microscopes provide faster measurements for a low magnification range at the cost of reduced height resolution.
Both types of measuring profilometers include a number of common components, such as lenses, which are generally expensive. In the non-interferometric mode, the interferometer may also be used as a traditional imaging microscope.
US 2007/0165241 relates to a profilometer which is used in the interferometric and the non-interferometric modes using expensive components for both types of measurements. The apparatus uses two types of objectives; one is adapted for use in interferometric measurements and the other is adapted for use in non-interferometric measurements. The apparatus includes the objectives in addition to lenses for directing light from a light source to the surface of the object.
Since the apparatus requires two objectives, the apparatus is expensive and needs a substantial volume for the two objectives. Further, since one objective is used for the interferometric measurements and the other is used for non-interferometric measurements, the apparatus need a mechanism for exchanging the objectives, e.g., a turntable. Such mechanism is a complex construction and requires an accuracy of positioning the objectives. Moreover, the apparatus needs pattern means located between a light source and a first optical means for applying a pattern to the light emitted by the light source when the apparatus is used as a non-interferometric measurement apparatus. The pattern means, however, is unnecessary for a viewing microscope.
U.S. Pat. No. 5,122,648 relates to a profilometer adapted to be used in an interferometric mode and in a non-interferometric mode. The profilometer includes a small reference mirror located concentrically in an objective. The mirror, however, is covered by a screen inserted into the objective in the non-interferometric mode. The mechanical cover of the mirror is a mechanical cumbersome solution.